CLASSIFICATION OF FISHES 23 



The so-called Acanthopteri are spiny rayed fishes including the 

 dominant Perch, Bass group (IX and X), and all those forms with clearly 

 traceable relationships to it; as the Mullets, etc. (VIII) related to its 

 probable immediate ancestors (indeed these ancestors may well have 

 been very much like the Pirate Perch) ; or the derivative Mackerel-like 

 fishes (XI) (an adaptation to wide ranging habit over open seas). 

 Another clearly marked line (XII) is through the Angelfish (beginning 

 with the Wrasses, which, superficially at least, are more Perch-like than 

 the Mackerels, ending with the very un-Perch-like plectognath fishes, 

 which might be considered the apex of specialization in fish life). The 

 Sculpin-like or mail-cheeked fishes (XIII), although a well marked 

 group, have certain members of sufficiently Perch-like character to show 

 their derivation. The Gobies, Blennies, etc. (XIV) are probably one or 

 several lines unrelated to this one, although it is conceivable that they 

 arose through more or less Sculpin-like forms. At the other end of this 

 series there is an approach to the Codfishes (XV). Recent investigation 

 and recently discovered fossils have shown that the very remarkable 

 Flatfishes (XVI) were derived rather directly from Perch-like fishes. 

 The final section, the Frog Fishes (XVII) would seem to have been 

 evolved from Perch-like ancestors, either directly or through Sculpin, 

 Blenny or Goby-like forms. 



The following artificial key to the families of our fishes (based only 

 on those species which occur locally) may be found useful by the student. 



I. A round sucking terminal mouth with concentric rows of 

 teeth. Body eel-like. Petromyzonidce 







II. Mouth transverse on the lower surface of head. Skin of 

 body continuous over the fins. Scales spine or nodule-like, 

 usually minute, sometimes absent. 



1. Not notably flattened horizontally, tail fin unsym- 

 metrical, the upper lobe the longer. 



A. Head peculiar, broad, flat, hammer-shaped. 



Sphyrnidoe 



B. Upper lobe of tail excessively long. Alopiida 



C. A spine at the front of each of the two back fins. 



Squalidce 



D. Not as above. 



a. Peduncle usually without a keel on the side. 

 Tail fin notably unsymmetrical, not lunate. 



